The subject matter of the invention is 2-silacoumaranes of the following formula ##STR1## in which X represents halogen moieties and/or alkyl or fluorinated alkyl moieties of 1 to 4 carbon atoms, R' represents chlorine moieties or alkoxy moieties of 1 to 4 carbon atoms and R identical or different alkyl moieties of 1 to 4 carbon atoms; a represents 0 or 1 or 2.
Further subject matter of this invention is a method of preparing the claimed cyclic phenol organosilane esters by esterification of corresponding o-allyl phenols with hydrogen silanes of the general formula IV EQU HSiR.sub.2-a Cl.sub.a+1 (IV)
to form corresponding o-allyl phenolsilane monoesters of the general formula II ##STR2## in which X, R and a have the meaning given above, for which patent protection is sought as new forms of matter, followed by cyclization of this allyl phenol silane monoester.
In German Pat. No. 22 37 961 chlorophenoxysilanes are described which have a bioresistant action which they retain even after incorporation into plastics. A disadvantage in these compounds is the vapor pressure of these compounds, which is too high for practical purposes and in some cases exceeds the maximum allowable concentrations.
The problem therefore existed of finding phenol organosilane compounds which have a bioresistant action and have a very low vapor pressure. Furthermore, the compounds sought are to have a maximum of four chlorine atoms on the phenol ring, and if possible they are to have the desired properties even if the aromatic ring is substituted with only two or three chlorine atoms.